You should already have a DPA officer. The reality is that not much has changed between the DPA and the GDPR except the fine has increased massively. Markbooks or seating plans with names associated with any type of detail on has always been against the DPA and your school could have been prosecuted for it. Someone mentioned on facebook about their books having the pupils grades on, that is also against the DPA/GDPR; target grades should not be on the front of their books, all their details should be kept secure. We might think that it is picky, but would you like to see the HT walking around with your observation grade or pay scale wrote on it? Nothing should be printed out with a pupils name on it with any detail about them, if you have to make a code up that you can recognise; e.g red for pupil premium and yellow for EAL.